U.S. Pat. No. 4,051,267 to Jongeling, issued Sept. 27, 1977, discloses that carrageenans are particularly suitable for suspending and stabilizing tannins (polyphenols) in a tea extract which is transported in a frozen or chilled condition for use in vending machines. ThepH of the tea extracts used appears to be at least 4.9 based on the Examples. Jongeling also teaches that good suspension and stabilization can be obtained with xanthan gum. However, Jongeling found that even small amounts (less than 1 g. of xanthan gum per 100 ml. of tea extract) increased the viscosity of the tea extract so that the accuracy of dosing in the dispensing machine was impaired.
U.S. Pat. No. 2,963,368 to Greenbaum, issued Dec. 6, 1960, discloses the use of small proportion of a suspending agent, such as cellulose gum, a solubilizer, such as glycerol, or both, in a tea concentrate to prevent precipitation of remaining caffeine and tannin constituents. The tea concentrate is prepared from a tea extract having a total solids content of 11 to 12% and a pH of 4.8 to 5.0. The tea concentrate is preferably raised to a pH of 5.5 by adding sodium bicarbonate and is protected from microbial growth by the inclusion of sodium benzoate.